(CNN) -- Before returning to the States this weekend, I and others in my family spent enthralled hours at the Churchill War Rooms in London, along with the new museum in his honor next door. Now, there was a leader! There was a man whose example shouts out to us now in our hour of trouble.

On both sides of the Atlantic, the turmoil of this past week has sparked cries for those in political power to step up and for God's sake, lead. Fears are spreading across Europe as well as the U.S. that not only are our economies teetering but our politicians are ineffectual.

In their summit a short while ago, leaders of European democracies promised they had fixed the problems of their weakest player, Greece. Instead, their solution was so timid that fears of default have spread to Italy and Spain, the third and fourth largest economies in the euro zone. In the U.S., President Obama and Congressional leaders assured us that their budget deal would put us on a safe path. Instead, markets plunged and Standard & Poors stripped our county of its AAA credit rating for the first time ever.

It's not that you don't have the economic capacity to pay your bills, said S&P; we're just not sure you have the political capacity to pay them. One can well object to the decision, as the White House has, but the damage is done in international eyes. Gloom is thick across the waters.

Winston Churchill would have rejected this pessimism in an instant. He was offered the prime ministership in May 1940 when Hitler had marched across much of Europe and chased British troops off the mainland. Many of Britain's older political leaders were so despondent they wanted to capitulate to Hitler and had signed a peace treaty.

Churchill rallied younger ministers, turned around the cabinet, and inspired his people to fight to the end. He had few weapons but, as it was said, he mobilized the English language and sent it into battle. What we would give for leaders today who are as defiant in the face of trouble.

Churchill also understood the importance of banishing fear and steadying a country. The war rooms are the fortification where he, his ministers, military advisers and secretaries worked belowground, as German bombs rained down on London streets. In taped interviews, those who had duties there spoke of cramped quarters, short rations, long hours and claustrophobia -- but to a person, they dismissed that as nothing. Churchill drove them hard and could be overbearing, but they loved him for his courage and resolve. (Stiff upper lips, chaps!)

On several walls hang posters from those days: "Keep Calm & Carry On." That is very much the spirit that leaders of today need to instill in peoples across the Atlantic. They must replace fear with faith in the future.

In Europe and especially in the U.S., the public is disgusted with politics because their leaders squabble like kids in a sandbox. Churchill lived in a day when there were bitter fights too. But upon taking the reins, he immediately formed a coalition government.

We must not let our arguments over the past dominate the present, Churchill said, or we will lose the future. There in the war cabinet room, one sees chairs reserved for Labor as well as Conservative ministers -- coming together, they could stop Hitler. Isn't that a lesson for us today, too?

Finally, Churchill understood the importance of a leader raising a banner, setting clear goals and marching out in front -- especially in a crisis. None of his advisers would have ever said he "leads from behind;" that was inconceivable. Nor would he, as the European Central Bank has just done, have ever said that his approach to a problem was one of "constructive ambiguity." Who can take confidence in that?

Churchill had his flaws -- he was human. But his leadership turned Britain's darkest hour into its finest hour. Can our American and European leaders please schedule their next meeting in his war rooms?

The opinions expressed in this commentary are solely those of David Gergen.